Composition useful as gum inhibitor for motor fuels



Feb 7, 1950 M. R. BRIMER 2,496,930

COMPOSITION USEFUL AS GUM INHIBITOR FOR MOTOR FUELS Filed July 9, 194eEffect/vengas Effectiveness Mans/7a NTOR Effectiveness Patented Feb. 7,.1950.

COMPOSITION USEFUL AS GUM INHIBITOR FOR MOTOR FUELS Marshall R. Brimer,Kingsport, Tenn., assigner to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey Application July 9, 1946, Serial No. 682,248

This invention relates to a composition useful as a gum inhibitor formotor fuels and to motor fuels stabilized against gum formation.

It is well known that many motor fuels which are produced to possess ahigh octane rating are susceptible to deterioration during storage,owing to a tendency to react with atmospheric oxygen. The result of theoxidation-is formation of gum which may actually render inoperable themotor in which the fuel is used. and in any event the fuel loses inoctane rating. Certain substances are known to act to prevent or inhibitoxidation of deteriorable motor fuels when added to the fuels inrelatively low concentrations. The addition of the inhibitor to themotorfuel must be made as soon as possible in order to achieve the maximuminhibiting effect. Therefore, the addition of the inhibitor iscustomarily part of the manufacturing process and is carried out at therefinery. l

- v4The practical use of gum inhibitors places cer tain limitations uponthe properties of such substances which may be considered for practicaluse. Of primary importance, of course, is the effectiveness of a givensubstance as an inhibitor of gum formation in the motor fuel.

However, substances possessing high effectiveness as inhibitors of gumformation in motor fuels must have certain 'additional properties inorder to be of practical use. The inhibitor should be a liquid, in orderto permit ready blending with the motor fuel.

A typical example of a highly eiiicacious gum inhibitor isN,N'diisopropyl p phenylenediamine (hereinafter sometimes called DIPDA).DIPDA is a solid and must be dissolved in a suitable solvent beforeblending with the motor fuel, e. g. isopropyl alcohol or toluene. Thegum inhibitor effectiveness of solutions of DIPDA in these commonlyemployed solvents is directly proportionalA to the concentration of theDIPDA 7 Claims. (Cl. 252-401) in solution, the solvent havingsubstantially no gum inhibitor effectiveness.

I have now found that by mixing DIPDA with at least one primary aromaticmonoamine of the benzene series which is devoid of -XH groups wherein Xrepresents a divalent atom, a composition is obtained, which, whendissolved in a solvent having substantially no gum inhibitoreffectiveness, e. g. isopropyl alcohol or toluene, gives an inhibitorsolution which has an effectiveness substantially greater than asolution of only DIPDA in the same solvents containing the sameconcentration of DIPDA. This is surprising, since primary aromaticmonoamines of the benzene series devoid of XH groups have only a slightgum inhibitor effectiveness, in and of themselves, in the concentrationsused in commercial practice. I have also found that primary aromaticmonoamines of the benzene series have the same synergistic effect onother N,N-dialkyl-pphenylenediamines, e. g. N,N di-secondarybutyl-p-phenylenediamine.

It is, accordingly, an object of my invention to provide newcompositions useful as gum inhibitors for motor fuels. A further objectis to provide motor fuels stabilized against gum formation with suchcompositions. Other objects will become apparent hereinafter.

In preparing my new compositions, I mix t\ gether to give an intimatemixture or solution, at least one N,N'dialkyl-p-phenylenediamine, e. g.N,N diisopropyl p phenylenediamine, N,N'disecondary butyl pphenylenediamne, etc., and at least one primary aromatic monoamine ofthe benzene series, e. g. aniline, a toluidine, a xylidine, etc. In mymore useful compositions, the primary aromatic monoamine of the benzeneseries constitutes from about 0.5 to about by weight of the mixture.Primary aromatic monoamines of the benzene series containing onlycarbon, hydrogen and of aniline.

nitrogen atoms are advantageously employed. The resulting mixture visadvantageously dissolved in a solvent before blending with the motorfuels. Typical solvents include methyl, ethyl, n-propyl, isopropyl,n-butyl and isobutyl alcohols,v n-propyl ethyl ether, n-propyl isopropylether, diisopropyl ether. di-n-propyl ether, benzene, toluene, xylenes,heptane, mixtures of petroleum hydrocarbons, e. g. straightrun gasoline,etc. These solvents are inert solvents, i. e. they have substantially nogum inhibitor eectiveness, in and of themselves and substantially nosynergistic effect on the zum inhibitor effectiveness of theN,N'dialkylp phenylenediamines.

'I'he eifects which I obtain in practicing my invention can beillustrated first with reference to a solution of DIPDA in. isopropylalcohol or toluene. The gum inhibitor effectiveness of such solutions ofDIPDA in a standard reference gasoline is represented by curve A in Fig.1 of the accompanying drawing. (As used herein, the effectiveness of aninhibitor is defined as the number of pounds of a standard comparisonmaterial required to produce the same induction period in an oxygenbomb-test as is produced by one pound of the inhibitor being tested, theoxygen bomb test being that described by Eglo, Morell, Lowry and Dryerin Ind. Eng. Chem. 24, 1375-1378, 1932.) The scale vused in Fig. 1 issuch that the effectiveness of a 50% (by weight) solution of DIPDA inisopropyl alcohol or toluene is 1.0. On this scale the eil'ectiveness ofthe isopropyl alcohol solution of N-butyl-p-aminophenol. which iscommonly used as a commercial gum inhibitor for motor fuels, isapproximately 1.0. Curve A of Fig. l shows that, for example, a 75%solution of DIPDA in isopropyl alcohol or toluene possesses aneffectiveness of 1.5, and a 25% solution of DIPDA in the same solventspossesses an eilectiveness of 0.5. In other words, the effectiveness ofDIPDA solutions in solvents known to the art is equal to theeffectiveness of pure DIPDA multiplied by the concentration of DIPDA inthe solution, when the DIPDA concentration is expressed as a fraction ofthe weight of the solution in question.

Comparing the above DIPDA solutions with solutions of DIPDA in aniline,the DIPDA solutions in aniline possess effectiveness far in excess ofthat calculated by multiplyingthe effectiveness of pure DlPDA by theconcentration of DIPDA in the aniline solution, yet the effectiveness ofaniline alone as a sum inhibitor is less than 0.05.

Curve B in Fig. 1 of the accompanying drawing gives the eectiveness ofsolutions of DIPDA in aniline in the same standard reference gasoline,and it will be seen that curve B departs greatly'in a positive directionfrom curve A. The shape of curve B can be explained if the presence ofaniline enhances the effectiveness of DIPDA, or if DIPDA enhances theeiectiveness The unexpected nature of my discovery can be more clearlyunderstood if the difference between curve B and curve A is ascribed toinhibitor effectiveness exerted by aniline in the aniline solutions ofDIPDA. For example, at a given concentration of DIPDA, the diilerencebetween curve A and curve B represents the 'inhibitor effectivenesscontributed by the aniline in the solution. When the effectivenesscontributed by the aniline is divided by the weight fraction of theaniline in the solu- 55 wise, in the group ha tion, the quotientrepresents the apparent inhibitor eectiveness of the aniline in thesolution. Representative values are as follows:

wenn: rmcwn Apparent Effectiveness mrns Annina f Anm 0.00 1.00 0.00 .a0.10 0.44 .so .so 0. s4 .1o .a0 1.43 .so .so 1. 70 .o0 .i0 1.80

Thus. when aniline is mixed vwith DIPDA, the effectiveness of theaniline appears to increase from less than 0.05 to more vthan 1.80, anincrease of more than 3600 per cent.

As pointed out above, a practical inhibitor should be liquid, in orderto facilitate blending with the motor fuels. Not only shouldthevinhibitor be liquid, but the liquidfshouldfnot be susceptible tofreezing at temperatures normally encounteredin retlnerles, and if the jinhibitor is .susceptible tofreezing above 10 C., its freezl ing pointmay.' handicap its practicability.v

I measure the freezing point of an inhibitor by cooling it to atemperature below its freezing point, inducing the formation of solid(by agitation or seeding), and then allowing the temperature of theliquid-solid mixture to rise slowly. I record the temperature at whichthe solid disappears as the freezing point.

In order vto vshow the' importance of this invention, I lhave preparedTable I (see below) Awhich shows howthe freezing points of practicalinhibitors caribe improved by taking advantage of the fapparenteffectiveness of aniline. Table I shows seven groups of five solutionseach, the

solutionsV being grouped laccording to inhibitor eectiveness. Theiirstfour columns of Table I show the` composition of the solutionswhich were tested, the fifth column shows the effectiveness of thesolutions, andthe sixth column shows the,

freezlngpoint of the solutions. Pure DIPDA is included ,forcomparisom Ineach group, it will beobserved that,the inhibitors which Vdo not con-vtain anilineehav'e freezing points which are much higher thanthefreezing'point of the inhibitor solutions which do aniline. Forexample in:v theV group.L whichffhasg/anc iectiveness of l 1.6'. the'lowering of` the ,-ireezingrpoint, made possible by utilizing'thisidisco the freezing point of arr-inhibitor can be achievedwithoutsacriicefof inhibitor potency, as'would be necessary ifthefreezingpolnt wereimproved by the use of other solvents. Likewise. TableI showsthat if it-be desired to 'maintain a lcertain maximum freezing"4point,the effectiveness can be greatly increased. Ifgforexample,10-C.'is set as the maximum practical allowablev freezing point, withoutusing aniline, the attainable eil'ectiveness is 0.9 l`(45% DIPDA+`55%toluene, freezing point 9 C.) or 0.7 (3,5% DIPDA-,-65% isopropylalcohol. freezing pointe C.) but by using my invention, the`attainableeffectiveness `.can be raised to 1.4',(either"53%-DIPDA-20%isopropyl alcohol-27% aniline, `freezing point 10 C. or

53% DIPDA20% toluene-27% aniline, freezing Thus the attainableeffectiveness point 6 C), lower 20% separation temperature" with thesame effectiveness as inhibitors prepared accordcan be doubled using myinvention.

Table I ing to the prior art. For example, if an inhibitor with aneiectiveness of 1.0 (comparable to ln- .eS. o...... )1..8 n. .dalbwcmauecwmsmw mm a s e a 05o. ulm .owoohmtv 8mm. 94.42 4015 15874569.. 8.54.0 Mmznl wwofa .w MMTNCMPMDWW hafpan mmm 1 1 n 1 a n 1. a I oi ammwmmamgwmawmmm Wa. d e 1 .1 p y 2 DS S e dav; mm%mm%e% mime f a b.pws anUXoxmmAr .edqo Nu 0 6066 4444 2222 1111 0000 9999 7777 )mm V,.un-um llm DMCW e mm 2. LLLL .LLLL LLLL LLL,... 1.11.1. 0.0.0.0. 000.0am etOhMWAemAaAEmmu.eW E e m .th2Dh1 DDonshn g nn .m0 PtaS% 0C @eta e am.1.m% ISM-.lm7)ydhgv H .m 0 00 0 O70 5 n ymzdannapznometmm e m m soa 2.a 020% nana nana nana onen a ai elm im uam.. w a. A a lpAmwla/s ao4aawm a w a mnpowmnwawhsi. terni T y m t e mmmqo( C. m m 0 00mm OOMM 00M@006% DOWN 00%.41 OCMW 1 l t mc. afnnluw a a .n 00 .1 no e ).1 AdOb r 0c2 n when nh a 1 p 7%A4 bur DA .a y mlm m wemmonhnmwmwwaDmw m www o annomavo @woo anon anon nooo waoo i n1(1=. t no. P mu c r s .m mmamwaba a I...a mmcamndwamaaaznuem a m A a n o la D. can o .D mm5%.wmee%mm wrommm cn m @www mama mama aan mama nana aman n a l minnpmamaawemmaa D 5 m n a.a a a 0. e m a .r L .n at. nmmwomewdmwnmw .MDC 874 06 64 2 2 .1.0litrulomri. Otanmr mm. a all am? ma a 1. s all... a: ii mamammmfmaaagwmaer us arun gywraghcwko mmwmi, m s s... n m Hmomdm ESWDM .W 0 6660644.4.4.4 22222 131111 00000 00099 77777 nWC m mw a LLLLL LLLLL LLLLLLLLLL LLLLL 0.0.00.0.. 0000.0. auta mn.md amm n P alum m.. E firm onwooamammna O aMMZl e hSWE e V..pguein Yeurn%t.k d tcemmmeuhmmoodm, 0 oDouma nonna otaaa enana ooaa comma nonna ummpnsfihat s n2 nt ,n awpaaomtmamaa Sem e t .l I d rf.. w meymmmtammtewmeaowm v. n apr stnmsmetwao m m 0 O,m00w 0%00@ 040200@ OOOw OwOOQ OMOO OMOOW Wxamm S w T mwmmmwrmndmtmw .wmm r l Msnrml .mi0nmvem5-tew a plmmnmmaama pwdts m. o@DONO wOOmO mOOmO 6.000%0 MOOQW OOUO MOOW manif.. mn e 8% .h A J mat fteS urwo 1 .m uwpawosmhepimmamw e. w l mramanmaammwgmm 0 D O .1. dpO y ean 61V... c u m naamw mmaa wanna wanna maman aman naman @mw/0m umanmmmmmmmmwm D r0.1 000 m mapamtaadnmmsm corded as the 20% separationtemperature.T from by invention can be seen at once. If it is By takingadvantage of the present invention. 60 desired to prepare an inhibitorwith an effective'- it is possible to improve the 20% separation nessequivalent to commercial inhibitors now temperature greatly. Table II(see below) comcommonly used, for example, an effectiveness of pares the20% separation temperature o f a 1.0, by using my invention very greatsavings can number of groups of solutions of DIPDA. e be achieved, inaddition to attaining greatly imsolutions within each effectivenessgroup in Iable 65 proved properties already described. It is obvious IIare arranged in order such that a solution that an inhibitor containing37% D1PDA-42% containing no a-niline can be readily compared isopropylalcohol or toluene- 21% aniline,ismuch with the solution containinganiline, and it will be seen that in every case (except where thecheaper than one containing 50% DIPDA-50% isopropyl alcohol or toluene,but the effectiveness 20% separation temperature" is below 50 C.) 70 ofboth is 1.0. This is true because DIPDA conthe lowering of the 20%separation temperatent of the inhibitor solution can be reduced fromture" is 13 C. or more. In other words, gum 50% to 37%, a saving of 26%of the most exinhibitors prepared according to my invention pensivecomponent of the solution. In other can be made to possess a highereiectiveness with words 13% of DIPDA and 8% of inert' solvents the same20% separation temperature" or a 76 have been replaced by 21% of anilinewithout line.

Yet another important advantage to be derived from the use of myinvention is the improvement `rwhich can be attained with respect tocolor sta- Y bility. The color stability of the inhibitor is importantfrom the standpoint of practical use. Inhibitor and inhibitor solutionscommonly are in contact with air before and after addition to motorfuels If an inhibitor under consideration is found to produce strongcolor upon atmospheric oxidation, it is said to lack color stability,and if it does not produce deep color upon atmospheric oxidation, it issaid to be color-stable. Inhibitors which show color instability areordinarily not suitable for practical use because the color producedinterferes with the saleability of the motor fuel. an inhibitor byobserving the shade and depth of color produced when one ounce of freshinhibitor is allowed to stand in a Z-ounce bottle, in the neck of whichis fitted a stopper bearing a, 1-inch length of 0.5 mm. tubing to permitaccess of air to the interior of the bottle. If a strong colordevelopsupon a few hours exposure. the inhibitor is unsatisfactory forpractical use, while if the inhibitor merely darkens after standingseveral days, it is satisfactory for practical use.

Heretofore. DIPDA has not been used commercially as an inhibitor becauseof the fact that it lacks color stability when dissolved in solventscommonly used in the art. An isopropyl alcohol solution of DIPDA becomesvery dark in color after only a few hours, even though the exposure ofthe solution to atmospheric oxygen has been slight. On the other hand,solutions of DIPDA in isopropyl alcohol and aniline are color-stable forseveral days, even when exposed continuously to atmospheric oxygen bythe procedure described above. As little as aniline in the solution isadequate to provide color stability and, since larger proportions ofaniline are desirable in order to take full advantage of my inventionwith regards to other desirable properties described herein, colorstability is no longer a problem with DIPDA when my invention is used.

It has been found that other aromatic amines are useful in practicing myinvention. For example, curves C and D in Figure 2 of the accompanyingdrawing show the effectiveness of DIPDA solutions in inert solvents,such as, isopropyl alcohol and toluene compared with solutions of DIPDAin o-toluidine. The other important properties, such as, freezing point,20% separation temperature, and color, as well as cost, are improved 'bythe use of o-toluidine in the manner similar to aniline. The xylidinesare likewise effective when used in accord-ance with my invention.

Other substituted phenylene diamines, such asN,N'di-secondary-butyl-p-phenylene diamines are also effective inpracticing my invention when used with the aromatic amines describedabove. For example, curves E and F in Figure 3 of the yaccompanyingdrawings shows the comparison between effectiveness of solutions ofN,Ndi secondary-butyl-p-phenylene diamines in inert solvents, e. g.isopropyl alcohol or toluene, and the effectiveness of mixtures ofN,N'disecondary butyl-p-phenylenediamine in aniline. Other importantproperties, such as, freezing point, 20% separation temperature, andcolor, are effective I measure the color stability of i'ful. dissolvedin an inert solvent to give a solution advantages in this case also. Asin 'the case of DIPDA, the toluidines and the xylidines behave in asimilar manner as aniline does.

As set forth above, primary aromatic monoamines of the benzene seriescontaining -XH groups, wherein X represents a divalent atom, areexcluded from my invention. Thus, p-hydroxy aniiine (p-aminophenol)p-mercapto aniline, etc. are excluded, but o-anisidine, m-chloroanlline,etc. are included;

Of my new compositions comprising a mixture of at least oneN.Ndisecondary alkyl-p-phenylenediamine and at least one primaryaromatic monoamine ofthe benzene series which contains only carbon,hydrogen and nitrogen atoms, those in which the nmonoamine constitutesfrom about l5A to 45% by weight of the mixture are especially Suchcompositions are advantageously containing from about 20 to about 45% byweight of the inert solvent.

My invention is directed to the stabilization of hydrocarbon motor fuelsagainst deterioration. By the term hydrocarbon motor fuel, I mean notonly motor fuels constituted entirely of hydrocarbons but also motorfuels containing hydrocarbon and appreciable amounts of othercombustible substances, such as alcohols. Cracked gasoline, as is wellknown, has an undesirable tendency to undergo deterioration uponstorage. Straight-run gasolines, on the other hand, do not have the sameundesirable tendency to deteriorate, although blended stock containingcracked gasoline and straight-run gasoline usually show thel undesirabletendency to deteriorate. It is to the stabilization of any unstableliquid motor fuels comprising light hydrocarbons and normally tending todeteriorate that my invention is directed. To stabilize motor fuelsagainst deterioration with my new composition, I dissolve a small amountof the composition in the motor fuel. Ordinarily an amountsufllcient togive a concentration of from about 0.000l% to about 0.1% (by weight) ofthe composition in the motor fuel will suflice to give a motor fuel ofsuitable stability against deterioration. Of course, the quantity of anyone of my new compositions which is actually employed will depend uponthe nature of the motor fuel being stabilized and the conditions underwhich the fuel is stored. The tendency of the motor fuel to'form gum canbe determined among other methods by an accelerated oxidation test. Thetest described by Egloff et al., supra, is very satisfactory and iswidely used. In accordance with this test, a sample of the motor fuelbeing tested, in an open 8ounce bottle, is placed in a suitable metalbomb surrounded by a water bath. Oxygen is introduced to pounds persquare inch ('7 kg. per square centimeter pressure). The bath is thenheated to 100 C. As the temperature increases, the pressure rises,reaches a maximum and continues near this maximum for a shorter orlonger period of time. 'I'he testis continued for 4 hours or until adrop in pressure is noted. The period from slightly before theattainment of maximum pressure (approximately 15 minutes from thebeginning of heating), until more than a slight drop in pressure takesplace (usually a sharp break in the pressure occurs), is recorded as theinduction period.

An induction period of less than 75 minutes is usually indicative ofvery low stability, while an induction of 300 or more minutes, forfreshly made motor fuels, represents a fuel possessing suitablestability for from 6 to 12 months storage in the northern half of theUnited States. For more southern or Warmer climates, the inductionperiod should be increased somewhat for satisfactory bulk storage ofabout one year duration.

My new composition can be employed to retard gun formation inhydrocarbon motor fuels which tend to undergo deterioration whether themotor fuel contains small or large amounts of addition agents, such astetraalkyl lead compositions. It is, of course, known that tetraalkyllead compounds, such as tetraet-hyl lead, are added to hydrocarbon motorfuels to improve the octane rating of the motor fuels. In some casesonly a relatively small amount of the tetraalkyl lead compound is added,but sometimes with certain aviation grades of gasoline, a larger amountis used, such as with aviation gasoline having an octane number above 80and comprising essentially non-gum-forming yhydrocarbons containing lessthan 1% by volume of oleflnic or diolenic hydrocarbons. Motor fuelshaving a relatively large amount of tetraalkyl lead compounds areusually referred to as heavily leaded gasoline.

Not only can my new compositions be used in all types of leadedgasoline, but my new compositions can, if desired, be added to the ethylfluid itself. Ethyl fluid usually is a solution containing a mixture oftetraalkyl lead compound and a halogenated hydrocarbon, such as ethylenedibromide or ethylene dichloride, or both. My new compositions serve toretard the formation of haze in ethyl fluid or in hydrocarbon motorfuels containing the "ethyl fluid, whether the hydrocarbon motor fuel isone which forms gum upon storage or is one which is composed essentiallyof non-gum-forming hydrocarbons.

What I claim as my invention and desire to be secured by Letters Patentof the `United States is:

1. A composition useful as a gum inhibitor for motor fuels consisting ofa mixture of a N,Ndi secondary alkyl-p-phenylenediamine in which eachalkyl group contains from 3 to 4 carbon atoms and a primary aromaticamine selected from the group consisting of aniline and o-toluidine, theprimary aromatic amine constituting 10 from about 0.5 to about by weightof the mixture. A

2. A composition useful as a gum inhibitor for motor fuels consisting ofa mixture of N,Ndi isopropyl-p-phenylenediamine and aniline, the anilineconstituting from about 0.5 to about 85% by weight of the mixture.

3. A composition useful as a gum inhibitor for motor fuels consisting ofa mixture of N,N'di secondary butyl-p-phenylenediamine and aniline, theaniline constituting from about 0.5 to about 85% by weight of themixture.

4. A composition useful as a gum inhibitor for motor fuels consisting ofa mixture of N,N'di isopropyl-pphenylenediamine and aniline, the anilineconstituting from about 0.5 to about 85% by weight of the mixture, themixture being dissolved in an inert solvent.-

5. A composition useful as a gum inhibitor for motor fuels consisting ofa mixture of N,N'di isopropyl-p-phenylenediamine and aniline, theaniline constituting from about 0.5 to about 85% by Weight of themixture, the mixture being dissolved in isopropyl alcohol.

6. A composition useful as a gum inhibitor for motor fuels consisting ofa mixture of N,N'di isopropyl-p-phenylenediamine and aniline, theaniline constituting from about 0.5 to about 85% by weight of themixture, the mixture being dissolved in toluene.

'7. A composition useful as a gum inhibitor for motor fuels consistingof a mixture of N,N'-di secondary butyl-p-phenylenediamine and aniline,the aniline constituting from about 0.5 to about 85% by weight of themixture, the mixture being dissolved in an inert solvent.

MARSHALL R. BRIMIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

2. A COMPOSITION USEFUL AS A GUM INHIBITOR FOR MOTOR FUELS CONSISTING OFA MIXTURE OF N,N'' -DIISOPROPYL-P-PHENYLENEDIAMINE AND ANILINE, THEANILINE CONSTITUTING FROM ABOUT 0.5 TO ABOUT 85% BY WEIGHT OF THEMIXTURE.